The present invention relates to a control device and relates to, for example, a control device of a motor.
In a brushless DC motor, as one of general control methods, on the basis of a rotating coordinate system in which a rotor magnetic pole direction is defined as a d axis and an axis which is advanced by 90° in the θ positive direction from the d axis is defined as a q axis, a d-axis current is set as 0, and linear control of a q-axis current and a torque is performed.
A technique of computing the rotation position of a rotor in the brushless DC motor on the basis of currents flowing in three-phase coils, not detecting the rotation position by using a sensor, is proposed.
Since the magnetic pole position (the position of the dq axis) of the rotor is unknown in a sensorless control including a method based on a current estimation error, the magnitude and the phase of an induced voltage generated in the motor are estimated and, from them, the magnetic pole position (the position of the dq axis) of the rotor is estimated.
For example, in Japanese Unexamined Patent Application Publication No. Hei 8(1996)-308286, current values Iu and Iv flowing in a stator coil are detected, and the rotation angle is estimated from the detected values. In Non-Patent Literature 1, “Sensorless Brushless DC Motor Control Method Based on Current Estimation Error”, Takaharu Takeshita, Naofumi Nomura, and Nobuyuki Matsui, T. IEE Japan, Vol. 115-D, No. 4, 1995, a sensorless brushless DC motor control based on a current estimation error is described.